Absorption of radio waves during a solar eclipse

Patel, D.; Kotadia, K. M.; Lele, P. D.; Jani, K. G.

doi:10.1007/bf02871864

Cited by 7 publications

(6 citation statements)

References 16 publications

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“…For the current eclipse, our GCP lied totally in the partial eclipse zone at an angle of 34° with respect to the path of totality and a large area of the Indian subcontinent was covered for the present study. It is also noted that the path lied totally under the equatorial ionization anomaly (EIA) region and few reports exist in literature over the Indian subcontinent [ Patel et al , 1986; Vyas et al , 1997; De and Sarkar , 1997; Abraham et al , 1998; Patra et al , 2009]. It is also interesting to note that the transmitter latitude 8.38°N was located almost near to the equatorial ionization trough region while our receiver was placed at 23.75°N latitude, which was near to the equatorial ionization crest region.…”

Section: Discussionmentioning

confidence: 64%

“…[ Dixit and Rao , 1980; Chandra et al , 2007]. Also, the influence of eclipses on the low‐latitude D‐region (i.e., over the equatorial anomaly region) is much less studied during ionospheric sunrise transition period [ Mechtly et al , 1969; Patel et al , 1986; Mendes da Costa et al , 1995; Clilverd et al , 2001]. A solar eclipse is similar to the onset of a short‐time night; therefore, the accompanying effects in both cases are normally expected to be similar.…”

Section: Introductionmentioning

confidence: 99%

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Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Guha

Roy

et al. 2010

J. Geophys. Res.

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[1] Changes in equatorial D-region electron density are studied using subionospherically propagating VLF signal at 18.2 kHz over a distance of 2200 km during the total solar eclipse of 22 July 2009. There are very few studies about the eclipse's effects on the equatorial lower ionosphere in the scientific literature. In the light of that, the objective of the present work is to study the effects of the eclipse on the dynamics of the equatorial lower ionosphere during ionospheric sunrise transition period. In the present case, great circle path between VLF transmitter and receiver falls totally in partial eclipse zone, having a maximum solar obscuration of 90% and an average obscuration of 74%. Results show an average decrease of 3.2 dB in signal strength compared to control days during peak solar obscuration over the path. A comparison with previous studies shows an increase both in lower ionosphere virtual reflection height (H′) and Wait inverse scale height parameter , respectively. During maximum eclipse over the path, the model profile shows an average 80% drop in electron density at a height of 71 km at equatorial lower ionosphere. A nonlinear variation of lower ionosphere electron density with solar radiation is found as opposed to the model study proposed by previous workers.Citation: Guha, A., B. K. De, R. Roy, and A. Choudhury (2010), Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal,

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Section: Discussionmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Guha

Roy

et al. 2010

J. Geophys. Res.

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“…For the solar eclipse of 16 February 1980, the field strength (11.8 MHz) measurements for the Colombo-Ahmedabad path showed an increase of about 23 db above the normal value during the totality (Jani et al, 1982). Multifrequency absorption measurements at Ahmedabad showed decreases of 40-45% (Patel et al, 1986). Phase and field measurements at VLF (16 kHz, Rugby) and HF (10 MHz ATA, New Delhi) and the field strength at LF (164 kHz, Tashkent) were also made at Kavalur in India during this event (Dixit et al, 1980).…”

Section: Discussionmentioning

confidence: 97%

Ionospheric measurements during the total solar eclipse of 11 August 1999

et al. 2007

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A number of radio experiments were conducted at Ahmedabad (23• N, 73• E) with the aim of studying the ionospheric effects of the total solar eclipse of 11 August 1999. Rapid radio soundings from the ionosonde were made on the eclipse day and on control days. A riometer was operating at 30 MHz, and Àeld strength measurements along the three oblique incidence paths of Colombo-Ahmedabad (11905 kHz), Bombay-Ahmedabad (558 kHz) and Rajkot-Ahmedabad (810 kHz) were also made. A reduction of about 20% was observed in the minimum frequency of reÁection from the ionosonde (f min ), which indicates a reduction in D-region ionization. The critical frequency of the E-layer was not measurable beyond 1600 h IST on eclipse day due to the strong blanketing sporadic-E, but there is a 20% decrease in the critical frequency of the F 1 -layer. Although there was no change in the minimum virtual height of the F-layer on eclipse day, there appears to have been a decrease in the height of maximum ionization (h p F 2 ) during the eclipse, indicating a reduction in the thickness of the F-layer. The signal strength of the Colombo-Ahmedabad path shows an initial rapid increase with the start of the eclipse (indication of a decrease in ionization in the D-and lower E-regions), but subsequently decreases until the maximum of the eclipse (excessive deviative absorption because of the wave penetrating to the E-region). The Àeld strength measurements of the Bombay-Ahmedabad path show a large fading after sunset as the sky wave also appeared. On eclipse day the fading started about an hour earlier. Riometer recordings also show a higher signal during eclipse day, which again indicates an eclipse-associated decrease in ionization.

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“…The relationship between the occurrence rates of tweeks and the increase in the intensity of solar eclipse at both the stations seems to be linear. However, a nonlinear relationship between ionization and solar radiation in the lower ionosphere has also been suggested [ Patel et al , 1986; Guha et al , 2010].…”

Section: Discussionmentioning

confidence: 99%

D-region ionosphere response to the total solar eclipse of 22 July 2009 deduced from ELF-VLF tweek observations in the Indian sector

Singh

Veenadhari²,

Maurya³

et al. 2011

J. Geophys. Res.

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[1] Observations of tweeks with higher harmonics (n > 1) at low latitude stations Allahabad and Nainital, in the Indian sector, during the total solar eclipse on 22 July 2009, are presented. Allahabad and Nainital stations were in 100% and 85% of the totality paths. Observations suggest that about 30-40% obscuration of solar disc can lead to the tweeks occurrence which otherwise occur only in nighttime. A total of 148 tweeks at Allahabad and 20 tweeks at Nainital were recorded with some of them up to 3rd harmonics. The World Wide Lightning Location Network data indicated that tweeks observed were generated by lightning's located in the partial eclipse area of Asia-Oceania region. The changes in D-region ionospheric VLF reflection height and electron density (∼22-23 cm −3 ) during eclipse have been estimated from the first cut-off frequency of the tweeks. The reflection height increased from ∼89 km from the first occurrence of tweek to about 91-92 km at the totality and then decreased to ∼87 km at the end of the eclipse, suggesting a change of about 5 km in the reflection height during eclipse. The reflection heights are lower by 2-3 km as compared to normal nighttime tweek reflection heights. The above increase in the reflection height indicate that the partial nighttime condition is created during eclipse, as the main D-region ionizing radiation Lyman a is blocked but solar soft X-ray and EUV radiations originating from the limb solar corona are not totally blocked which produce some of ionization in the D-region.

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Absorption of radio waves during a solar eclipse

Cited by 7 publications

References 16 publications

Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Response of the equatorial lower ionosphere to the total solar eclipse of 22 July 2009 during sunrise transition period studied using VLF signal

Ionospheric measurements during the total solar eclipse of 11 August 1999

D-region ionosphere response to the total solar eclipse of 22 July 2009 deduced from ELF-VLF tweek observations in the Indian sector

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